Actually, GPS would be the least of FEs worries regarding this matter.
We are talking about some thousands of satellites, operated both by governments of more than 50 different countries around the world and private business, . And used by more than 2 billion ppl atm for almost anything...XD
GPS validity is actually a most insignificant factor in the debate...especially since GPS acts only as a sender of information, whereas there are thousands of satellites ppl are sending info to, and thus know where exactly they are...^^